Déjà Vuniverse: Why some physicists think we could live in a Groundhog Day world

Roughly 13.8 billion years ago, all the energy in the universe was condensed into a one point. Until suddenly it was not. The resulting explosion was the largest explosion in all of the history of the universe, but from it, energy was formed in every matter, atoms, molecules, planets And eat life on earth.

This is the Big Bang Theory, a model that explains a lot of what we observe when we look at being. Among all the stars, galaxies, and clouds of gas is the cosmic background radiation—the heat leftover from the Big Bang, still faintly visible today, and one of the most striking evidences that the universe began from a single point. Measurements with multiple different instruments, including satellites and telescopes, indicate that these remnants are consistent with models of the explosive birth of our universe.

Even Albert Einstein toyed with the idea of ​​a universe going back and forth, dying and expanding, over and over again.

The universe is still expanding at a rate of 73 kilometers per second per megaparsec, a measure known as the Hubble constant. You can imagine how this works by visualizing Two points on a balloon. When the balloon is inflated, the distance between the two points will increase; Fill the balloon with dots, and everything seems to grow apart from everything else over time as the balloon inflates. If the universe is a balloon and the points are galaxies, that’s a good metaphor for how our universe has changed over time.

Many scientists predict that tens of trillions of years from now, the universe will eventually run out of steam and “freeze over.” This would be the heat death of the universe. Also known as the Big Freeze, this theory describes the ultimate fate of the universe as it approaches maximum entropy. When this threshold is reached, there is no more thermal energy or heat. Stars cannot undergo nuclear fusion, so there is no life.

But an interesting alternative, even if it doesn’t carry much scientific weight, is that before it’s all over, the universe can wind back down again – all the galaxies bunch together, spinning more and more instead, until they’re compressed back to a point. Astronomers call it the Big Crunch. (Big Bang, Big Crunch… I feel like a theme here.) In the distant future, as everything condenses, gets tighter and tighter, it could create the conditions for the Big Bang once again.

This is the basic premise behind the cyclic or oscillating universe theory, which actually dates back to the 1930s. Even Albert Einstein toyed with the idea of ​​a universe going back and forth, dying and expanding, over and over again. Not unlike the 1993 romantic comedy”hard day,” starring Bill Murray as a weatherman stuck in a time loop, living the same day over and over again, our world can cycle over and over through the various iterations. Crunch, bang, crunch, bang.

It was around this time that Richard Chase Tolman, an American physicist and cosmologist, was the first to really promote this idea, but initially set out to disprove it. In the early 20th century, the Big Bang theory was not dominant. Most people believe that the universe has always existed and always will exist. In fact, for many years, the “big bang” was used in an ironic way, a way Refusal How absurd the idea was for astronomers. But Tolman noted that the ratio of hydrogen and helium – the two most abundant elements in the universe – cannot occur in a static universe. The explosion most likely set things off.

In 1934, Tolman published Relativity, Thermodynamics, and Cosmology, inspired in part by descriptions of the expanding universe model first proposed by Edwin Hubble in 1929. Together, he and Hubble published a paper describing the expansion of the universe. It is quite clear that the stars and galaxies spread out as in our balloon metaphor. What was less clear to Tolman and other astronomers was whether or not gravity would eventually pull the universe together. “He took the possibility of the universe’s oscillation very seriously,” one of them said Personal Biography Who said Tolman.

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As the Big Bang became an accepted scientific theory, the oscillating universe theory died out. But some physicists, such as Paul Steinhardt and Neil Turok, have picked up the idea again, modified it somewhat and given it new life. The central part of the updated theory concerns dark energy, a mysterious and not fully understood aspect of the universe that is believed to be the driving force behind the expanding universe.

In their 2007 book “The Infinite Universe: Beyond the Big BangSteinhardt and Turok describe how they came up with this theory by positing that dark energy could have existed before the Big Bang and that it was so strong that it would eventually pull the universe back together using a “pulsating” motion that stretches the “branes,” a term used in theoretical physics. To describe some kind of structure in the universe.

If this is true, then our universe is in a seemingly endless loop, a cosmic version of Groundhog Day with a rhythm spanning billions or even trillions of years.

“Potential energy will not be noticeable again until after nine billion years of expansion have passed, and the density of matter and radiation has fallen below potential energy,” Steinhardt and Turk wrote. “Only then will the spring-like potential energy come back in again, just as it did before the explosion. Once again, it will act as a source of dark energy causing the expansion of the membranes to accelerate, which is exactly what we are witnessing today…..”

“Of course, if it happens once, there’s no stopping the whole process from happening again and again, and again and again. Eruptions can go on forever,” Steinhardt and Turok continued. “Suddenly and inadvertently, we’re resurrecting an old, impossible idea we’d learned: a circular universe.”

If this is true, then our universe is in a seemingly endless loop, a cosmic version of Groundhog Day with a rhythm spanning billions or even trillions of years. However, the theory is not widely accepted in science. It would be very difficult to test the oscillating universe theory, as no information would likely survive cycling through the Big Bang or Big Crunch, although mathematical physicist Roger Penrose has argued that Black holes from previous universes have escaped metamorphosis.

There are many models of the universe, but for a model to be useful it must be testable. The Big Bang theory is the best model we have of the entire universe, how it formed and where it’s headed. It could be completely wrong, however Good luck refuting that. But until we know more about dark energy – arguably the most mysterious constituent matter and energy in the universe – we may not have enough evidence to point to a repeating cycle of universal death and rebirth.

But interestingly, there may be other universes with different fundamental constants that have a periodic quality to them. Of course, the existence of other universes requires that the multiverse theory be true. Incidentally, while there are aspects of our universe that suggest we may live in a multiverse, so does this one It cannot be proven.

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